BTAB: Stairway To Heaven
Artist: Led Zeppelin
Album: Led Zeppelin 4
I've included bass lines for the parts with no bass for those of you who can't sit still and not play for 2 minutes. They are marked with a aterix (*). Just follow the low guitar parts.(thnx to Rattman)
Drop D Tuning
*Intro:
G---------------------------------------
D-7---6--5--4--3--3--3--5---------------
A---------------------------------------
D---------------------------5---7--7----
*Change:
G------------------------------------
D--------0~-3~-------------0~--------
A-0-2-3~-------0~---0-2-3~-------0-0-
D------------------------------5-----

 
Bass First enters at about 2:15 in the "It makes me wonder" part:
G-----------------------------------------------
D------------0----0----------------0-----0------
A-0---0---0---------0----0----0--0---------0----
D---------------------0----------------------0-0
"Theres a feeling..."
G----------------------------------------------------------------------
D----------------------------------------------------------------------
A-0-2-3-2-0~---0-2-3-2---0-0~------------------------------------------
D----------------------5-----------------------------------------------
Keep your bass very low through this part. These 2 patterns above continue until the drums enter at 4:19. 
"If theres a bustle..."
G----------------------------------------------------------------------
D----------------------------------------------------------------------
A-3~-2~-0--0-0--0-2-3~-2~---0~-----------------------------------------
D-------------------------5--------------------------------------------
"Makes me wonder..." part.
G----------------------------------------------------------------------
D----0---------------0-------------------------------------------------
A-0----0---------------0----(0)----------------------------------------
D----------0----0-0------0------(4-5-7)--------------------------------

                                
^ last time through
also its played like this sometimes
G----------------------------------------------------------------------
D-----------------0----------------------------------------------------
A-0--0--------------0--------------------------------------------------
D------3-0---0--0-----0-0--0-------------------------------------------

 
Break (5:50):
"ooooooowoooah..."
G-------|--------------------------------------------------------------
D-------|--------------------------------------------------------------
A-------|-5-5-5~----5-5-5~---5-5-5--5--5----5--3~----------------------
D-0~----|-0-0-0~----0-0-0~---0-0-0--0--0----0--------------------------

          ^repaeats
Guitar Solo(5:57):
G-----------------------------------
D-----------------------------------
A-0--0------------------------------
D-------5--5--5-3-3-3-3-3-3-3-3-35-

 
When the loud rythm guitar and screamed vocals come in, switch to this more structured riff:
"And as we wind on..."

G---------------------------
D---------------------------
A--------------------------
D-7-7---5-5--3--3--3--3-3-5-
This continues until the end.